1 /* 2 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk}) 3 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de) 4 * Copyright (C) 2004 PathScale, Inc 5 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 6 * Licensed under the GPL 7 */ 8 9 #include <stdlib.h> 10 #include <stdarg.h> 11 #include <errno.h> 12 #include <signal.h> 13 #include <strings.h> 14 #include <as-layout.h> 15 #include <kern_util.h> 16 #include <os.h> 17 #include <sysdep/mcontext.h> 18 19 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = { 20 [SIGTRAP] = relay_signal, 21 [SIGFPE] = relay_signal, 22 [SIGILL] = relay_signal, 23 [SIGWINCH] = winch, 24 [SIGBUS] = bus_handler, 25 [SIGSEGV] = segv_handler, 26 [SIGIO] = sigio_handler, 27 [SIGALRM] = timer_handler 28 }; 29 30 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) 31 { 32 struct uml_pt_regs r; 33 int save_errno = errno; 34 35 r.is_user = 0; 36 if (sig == SIGSEGV) { 37 /* For segfaults, we want the data from the sigcontext. */ 38 get_regs_from_mc(&r, mc); 39 GET_FAULTINFO_FROM_MC(r.faultinfo, mc); 40 } 41 42 /* enable signals if sig isn't IRQ signal */ 43 if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM)) 44 unblock_signals(); 45 46 (*sig_info[sig])(sig, si, &r); 47 48 errno = save_errno; 49 } 50 51 /* 52 * These are the asynchronous signals. SIGPROF is excluded because we want to 53 * be able to profile all of UML, not just the non-critical sections. If 54 * profiling is not thread-safe, then that is not my problem. We can disable 55 * profiling when SMP is enabled in that case. 56 */ 57 #define SIGIO_BIT 0 58 #define SIGIO_MASK (1 << SIGIO_BIT) 59 60 #define SIGALRM_BIT 1 61 #define SIGALRM_MASK (1 << SIGALRM_BIT) 62 63 static int signals_enabled; 64 static unsigned int signals_pending; 65 static unsigned int signals_active = 0; 66 67 void sig_handler(int sig, struct siginfo *si, mcontext_t *mc) 68 { 69 int enabled; 70 71 enabled = signals_enabled; 72 if (!enabled && (sig == SIGIO)) { 73 signals_pending |= SIGIO_MASK; 74 return; 75 } 76 77 block_signals(); 78 79 sig_handler_common(sig, si, mc); 80 81 set_signals(enabled); 82 } 83 84 static void timer_real_alarm_handler(mcontext_t *mc) 85 { 86 struct uml_pt_regs regs; 87 88 if (mc != NULL) 89 get_regs_from_mc(®s, mc); 90 timer_handler(SIGALRM, NULL, ®s); 91 } 92 93 void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc) 94 { 95 int enabled; 96 97 enabled = signals_enabled; 98 if (!signals_enabled) { 99 signals_pending |= SIGALRM_MASK; 100 return; 101 } 102 103 block_signals(); 104 105 signals_active |= SIGALRM_MASK; 106 107 timer_real_alarm_handler(mc); 108 109 signals_active &= ~SIGALRM_MASK; 110 111 set_signals(enabled); 112 } 113 114 void deliver_alarm(void) { 115 timer_alarm_handler(SIGALRM, NULL, NULL); 116 } 117 118 void timer_set_signal_handler(void) 119 { 120 set_handler(SIGALRM); 121 } 122 123 void set_sigstack(void *sig_stack, int size) 124 { 125 stack_t stack = { 126 .ss_flags = 0, 127 .ss_sp = sig_stack, 128 .ss_size = size - sizeof(void *) 129 }; 130 131 if (sigaltstack(&stack, NULL) != 0) 132 panic("enabling signal stack failed, errno = %d\n", errno); 133 } 134 135 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = { 136 [SIGSEGV] = sig_handler, 137 [SIGBUS] = sig_handler, 138 [SIGILL] = sig_handler, 139 [SIGFPE] = sig_handler, 140 [SIGTRAP] = sig_handler, 141 142 [SIGIO] = sig_handler, 143 [SIGWINCH] = sig_handler, 144 [SIGALRM] = timer_alarm_handler 145 }; 146 147 static void hard_handler(int sig, siginfo_t *si, void *p) 148 { 149 struct ucontext *uc = p; 150 mcontext_t *mc = &uc->uc_mcontext; 151 unsigned long pending = 1UL << sig; 152 153 do { 154 int nested, bail; 155 156 /* 157 * pending comes back with one bit set for each 158 * interrupt that arrived while setting up the stack, 159 * plus a bit for this interrupt, plus the zero bit is 160 * set if this is a nested interrupt. 161 * If bail is true, then we interrupted another 162 * handler setting up the stack. In this case, we 163 * have to return, and the upper handler will deal 164 * with this interrupt. 165 */ 166 bail = to_irq_stack(&pending); 167 if (bail) 168 return; 169 170 nested = pending & 1; 171 pending &= ~1; 172 173 while ((sig = ffs(pending)) != 0){ 174 sig--; 175 pending &= ~(1 << sig); 176 (*handlers[sig])(sig, (struct siginfo *)si, mc); 177 } 178 179 /* 180 * Again, pending comes back with a mask of signals 181 * that arrived while tearing down the stack. If this 182 * is non-zero, we just go back, set up the stack 183 * again, and handle the new interrupts. 184 */ 185 if (!nested) 186 pending = from_irq_stack(nested); 187 } while (pending); 188 } 189 190 void set_handler(int sig) 191 { 192 struct sigaction action; 193 int flags = SA_SIGINFO | SA_ONSTACK; 194 sigset_t sig_mask; 195 196 action.sa_sigaction = hard_handler; 197 198 /* block irq ones */ 199 sigemptyset(&action.sa_mask); 200 sigaddset(&action.sa_mask, SIGIO); 201 sigaddset(&action.sa_mask, SIGWINCH); 202 sigaddset(&action.sa_mask, SIGALRM); 203 204 if (sig == SIGSEGV) 205 flags |= SA_NODEFER; 206 207 if (sigismember(&action.sa_mask, sig)) 208 flags |= SA_RESTART; /* if it's an irq signal */ 209 210 action.sa_flags = flags; 211 action.sa_restorer = NULL; 212 if (sigaction(sig, &action, NULL) < 0) 213 panic("sigaction failed - errno = %d\n", errno); 214 215 sigemptyset(&sig_mask); 216 sigaddset(&sig_mask, sig); 217 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0) 218 panic("sigprocmask failed - errno = %d\n", errno); 219 } 220 221 int change_sig(int signal, int on) 222 { 223 sigset_t sigset; 224 225 sigemptyset(&sigset); 226 sigaddset(&sigset, signal); 227 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0) 228 return -errno; 229 230 return 0; 231 } 232 233 void block_signals(void) 234 { 235 signals_enabled = 0; 236 /* 237 * This must return with signals disabled, so this barrier 238 * ensures that writes are flushed out before the return. 239 * This might matter if gcc figures out how to inline this and 240 * decides to shuffle this code into the caller. 241 */ 242 barrier(); 243 } 244 245 void unblock_signals(void) 246 { 247 int save_pending; 248 249 if (signals_enabled == 1) 250 return; 251 252 /* 253 * We loop because the IRQ handler returns with interrupts off. So, 254 * interrupts may have arrived and we need to re-enable them and 255 * recheck signals_pending. 256 */ 257 while (1) { 258 /* 259 * Save and reset save_pending after enabling signals. This 260 * way, signals_pending won't be changed while we're reading it. 261 */ 262 signals_enabled = 1; 263 264 /* 265 * Setting signals_enabled and reading signals_pending must 266 * happen in this order. 267 */ 268 barrier(); 269 270 save_pending = signals_pending; 271 if (save_pending == 0) 272 return; 273 274 signals_pending = 0; 275 276 /* 277 * We have pending interrupts, so disable signals, as the 278 * handlers expect them off when they are called. They will 279 * be enabled again above. 280 */ 281 282 signals_enabled = 0; 283 284 /* 285 * Deal with SIGIO first because the alarm handler might 286 * schedule, leaving the pending SIGIO stranded until we come 287 * back here. 288 * 289 * SIGIO's handler doesn't use siginfo or mcontext, 290 * so they can be NULL. 291 */ 292 if (save_pending & SIGIO_MASK) 293 sig_handler_common(SIGIO, NULL, NULL); 294 295 /* Do not reenter the handler */ 296 297 if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK))) 298 timer_real_alarm_handler(NULL); 299 300 /* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */ 301 302 if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK)) 303 return; 304 305 } 306 } 307 308 int get_signals(void) 309 { 310 return signals_enabled; 311 } 312 313 int set_signals(int enable) 314 { 315 int ret; 316 if (signals_enabled == enable) 317 return enable; 318 319 ret = signals_enabled; 320 if (enable) 321 unblock_signals(); 322 else block_signals(); 323 324 return ret; 325 } 326 327 int os_is_signal_stack(void) 328 { 329 stack_t ss; 330 sigaltstack(NULL, &ss); 331 332 return ss.ss_flags & SS_ONSTACK; 333 } 334